Iron Metabolism

Iron is an essential trace element for humans that cannot be synthesised by the body. Therefore, it is necessary to ensure sufficient intake through the diet. In addition to well-known sources such as meat and meat products, many vegetables, legumes, and whole grain products also contain high levels of iron. Disorders of iron metabolism, particularly iron deficiency-related conditions, are widespread and associated with a range of clinical syndromes. Epidemiological studies in Europe show that 5-10% of the general population and around 20% of women of childbearing age have latent or pre-latent iron deficiency.

Iron is one of the most important trace elements for the body. Adequate iron intake supports numerous vital functions, including:

• Development and function of the immune system
• Formation of red blood cells
• Oxygen transport
• Energy metabolism
• DNA synthesis
• Development and function of neurotransmitter systems

Maintenance of cellular function

In addition to animal products like beef and pork, plant-based foods such as amaranth, oats, legumes, and dried fruit are rich in iron. Fortified fruit juices can also help meet iron requirements. However, iron from plant sources has lower bioavailability compared to iron from animal sources. Vitamin C enhances iron absorption by reducing ferric iron (Fe³⁺) to the more readily absorbable ferrous form (Fe²⁺), which can help counteract iron metabolism issues.

A negative iron balance initially leads to depleted iron stores. At this stage, although iron reserves are reduced, there is still enough iron for erythropoiesis (formation of red blood cells).

This stage is characterised by insufficient iron supply for erythropoiesis in the bone marrow (iron-restricted erythropoiesis), even though haemoglobin levels remain within the normal range. Ferritin levels may still reach up to 100 ng/l despite reduced iron stores, which can mask the deficiency.

At this stage, haemoglobin levels fall below normal, which results in classic iron deficiency anaemia with reduced haemoglobin.

MCV = mean corpuscular volume of erythrocytes, MCH = mean corpuscular haemoglobin of erythrocytes

MVZ GANZIMMUN offers current screening markers for routine diagnostics of iron metabolism disorders.

The determination of haemoglobin levels in the blood can only detect pronounced iron deficiency anaemia, but is not suitable for diagnosing pre-anaemic stages. Other routine markers used to assess iron storage status, such as the acute phase proteins transferrin or ferritin, are influenced by infections or inflammation. Therefore, they are only of limited use for monitoring patients with chronic illnesses.

Ferritin (also known as storage iron) is a protein complex the only function of which is to store iron. A distinction is made between intracellular ferritin and serum ferritin. Serum ferritin levels rise quickly in response to dietary iron, especially from animal sources. However, ferritin levels are only reliable in the absence of other conditions such as inflammation, infections, liver disorders, or malignant tumour disease.

Transferrin is a liver-produced iron transport protein. It binds absorbed iron in the intestinal mucosa and transports it to the bone marrow for haemoglobin synthesis. In iron deficiency, transferrin levels are elevated.

Low ferritin levels suggest depleted iron stores, but do not prove functional deficiency. Measuring the soluble transferrin receptor (sTfR) complements ferritin testing by assessing iron availability for cells. sTfR rises early in iron deficiency – before haemoglobin levels drop. The key advantage of measuring sTfR compared to ferritin is that the results are not influenced by patient-specific interfering factors. Thus, it allows for accurate differentiation between anaemia that is caused by iron deficiency and anaemia that is caused by chronic illness.

The ferritin index (sTfR/log ferritin) allows for a reliable assessment of iron reserves even in the presence of immune activity, liver disorders, or tumours. At MVZ GANZIMMUN, this index is automatically calculated free of charge when basic parameters (haemoglobin, ferritin, CRP, and sTfR) are requested.

^{Table: Overview of key parameters in iron diagnostics}